1. Technical Field
The present invention relates to an apparatus for detecting the state of a storage device, and more particularly to an apparatus for detecting the voltage of a battery pack, and the like.
2. Related Art
A hybrid electric vehicle or a pure electric vehicle has hitherto been equipped with a battery pack built by means of series connection of a plurality of blocks, each of which is made up of one cell or a plurality of series-connected cells, and an apparatus for detecting a voltage of the battery pack, and the like, has heretofore been known.
11-109005 A describes a configuration that includes a differential amplifier for producing an output voltage corresponding to a voltage across a secondary battery serving as a battery to be measured, a voltage-frequency converter for converting the voltage output from the differential amplifier into a frequency, and a microcomputer serving as detection means for detecting the frequency as a voltage of the battery to be measured; and that detects the voltage of the secondary battery by mere connection of one signal line to the microcomputer by use of the voltage-frequency converter.
However, when a voltage of each of blocks of the battery pack is detected by connecting the block to a detector such as a voltage-frequency converter (a V/F converter), or the like, a leakage current arises when the battery is out of use. In order to prevent occurrence of the leakage current, disconnection of the battery from the detection circuit is required. Further, another method using a flying capacitor is also available as the method for detecting the voltage of a battery pack. Since a plurality of expensive low-resistance photo-MOS relays are required to prevent occurrence of a leakage current, an increase in cost and the number of components is also entailed, which in turn poses difficulty in miniaturization of the battery pack. Moreover, if voltages of respective blocks can be acquired synchronously or at arbitrary timings, an advantage will be yielded.